Fuel pump

ABSTRACT

A fuel pump includes a housing having a cavity. The cavity has a rear surface, and a drive gear and driven gear are disposed in the cavity and in mesh with one another for pressurizing fluid. A floating wear plate and a fixed wear plate are disposed in the cavity and are in contact with the drive gear and the driven gear. A flow orifice is formed as part of the floating wear plate, and a portion of the pressurized fluid flows through the flow orifice to an area between the rear surface of the cavity and the floating wear plate, causing the floating wear plate to apply force to the drive gear and driven gear, and causing the drive gear and driven gear to apply force to the fixed wear plate, thereby compensating for any wear of the drive gear, driven gear, and wear plates.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application No. 61/208,179, filed Feb. 20, 2009. The disclosure of the application is incorporated herein by reference.

FIELD OF THE INVENTION

The present invention relates generally to spur gear pumps, and more particularly to spur gear pumps that are made to have very precise positive displacement for metering fuel in which the displacement volume of the pump is correlated to the number of rotations of the gears, for use in fuel injection systems.

BACKGROUND OF THE INVENTION

Pumps presently used in various high-pressure applications commonly employ a set of gears in mesh with one another with a simple wear plate (also called a “thrust plate”) on each side of the gears. The width of one of the gears and the combined width of both wear plates creates what is commonly referred to as the “stack-up” in the pump housing. In order for the pump to function properly, there must be a minimal amount of space (i.e. clearance) between the stack up and the depth of the gear cavity in the pump housing. Both wear plates and the gears must be very precisely fitted into the housing with a total stack-up clearance of about 0.0001 ( 1/10 of one-thousandths) of an inch clearance to 0.0003 inch; 0.0002 inches is typical.

A pump with about 0.0001 inches of clearance is the most desirable for precise fluid metering, but it is quite expensive to do such precision machining, hand lapping, and fitting. A pump with 0.0001 inches of clearance is also very susceptible to seizing, especially because of the dirt that comes in most commercial fuels. The output flow of these pumps falls off continuously over time as the wear plates and gear faces wear over the life of the pump. Therefore, it has been a goal in the racing fuel pump art to provide an easy to manufacture, long lasting, precision, high-pressure metering pump.

Additionally, spur gear pumps have a housing which includes a gear cavity that is generally oval in shape. Prior art pumps having an oval-shaped cavity have the concern of deflection versus internal pressure in both the axis across the long sides of the oval (vertical axis) and the axis through the round ends of the oval (horizontal axis). Prior art pumps will distort a significant amount along the axis across the long sides of the oval and very little along the axis across the round ends of the oval when subjected to internal pressure, even though most of prior art pumps have rather massive housings. These pumps typically use gear diameters of 1.250 inches to 2.250 inches. They also typically use four, six, or eight bolts located in a nearly symmetrical pattern around the center of the gear cavity to keep the cover attached to the housing, but this has not provided a sufficient solution for preventing distortion of the housing. Large dowel pins have been used in an attempt to use the strength of the front cover to hold the two long sides of the oval together, but this has shown little improvement.

Accordingly, there exists a need for a housing which undergoes minimal distortion when exposed to internal pressure. Also, there is a need for improved seals within the pump for it to operate optimally on gasoline.

SUMMARY OF THE INVENTION

The present invention is a high pressure fuel pump which incorporates a novel seal design on a floating wear plate. The fuel pump of the present invention includes a floating wear plate which is designed to accommodate seal swelling such that various fuels and additives may be used, which swell the volume of the seal, without affecting the operation of the pump.

The fuel pump according to the present invention not only pumps volume, but also creates the desired pressure required for the fuel system, from a few pounds per square inch (psi) to a range of 500-800 psi. The pump of the present invention is also light weight and compact for automotive and racecar use.

The present invention attains minimum distortion of the housing by using more fasteners, and more clamping force on each fastener, to clamp the cover so tightly to the housing that the long sides of the housing walls cannot move under the cover when pressure is present inside of the housing. The present invention has a housing which includes an oval-shaped cavity, and a total of twelve threaded studs (not dowels) are used, with six studs located along each of the long sides of the oval-shaped cavity. Studs allow more clamping force than bolts, and six along each side of the oval-shaped cavity are much more effective than a symmetrically spaced bolt pattern. This bolt pattern, combined with the high clamping forces, produces much less distortion due to internal fuel pressure than found in pumps incorporating prior art designs.

The present invention is a fuel pump with very precise positive displacement that is lightweight, for automotive and racecar use, with excellent durability. The pump design of the present invention accomplishes all of these objectives.

Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples, while indicating the preferred embodiment of the invention, are intended for purposes of illustration only and are not intended to limit the scope of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will become more fully understood from the detailed description and the accompanying drawings, wherein:

FIG. 1 is a perspective view of a pump according to the present invention;

FIG. 2 is a perspective view of a housing used for a fuel pump, according to the present invention;

FIG. 3 is a first perspective view of a floating wear plate having a side-seal, used in a fuel pump according to the present invention;

FIG. 4 is a second perspective view of a floating wear plate with the side-seal removed, used in a fuel pump according to the present invention;

FIG. 5 is a sectional top view take along lines 5-5 of FIG. 1;

FIG. 6 is a third perspective view of a floating wear plate used in a fuel pump, according to the present invention;

FIG. 7 is a side view of a fixed wear plate used in a fuel pump, according to the present invention;

FIG. 8 is a side view of a housing used in a fuel pump, according to the present invention; and

FIG. 9 is a perspective view of a cover which connects to a housing used in a fuel pump, according to the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The following description of the preferred embodiment(s) is merely exemplary in nature and is in no way intended to limit the invention, its application, or uses.

Referring to the Figures generally, a pump according to the present invention is shown generally at 10 (FIG. 1). The pump 10 includes an inlet 14 and an outlet 12, the inlet 14 feeds fuel into a housing 16 which has a cover plate, generally shown at 18.

The housing 16 (FIG. 2) includes a cavity, generally shown at 20, as well as a bore 22 (FIG. 5) through which a drive shaft 24 extends, and a recess 26 into which a driven or idler shaft 28 extends. The cover plate 18 also includes a first recess 30 which receives a first set of shaft support bearings 32, which support the drive shaft 24 on a first end 34. The cover plate 18 also has a second recess 36 which receives a first set of idler shaft support bearings 37 for supporting a first end 38 of the idler shaft 28. A second end 40 of the drive shaft 24 is supported by a second set of shaft support bearings 42 disposed in the bore 22 of the housing 16. A second end 44 of the idler shaft 28 is supported in the recess 26 by a second set of idler shaft support bearings 45.

When the cover plate 18 is attached to the housing 16, a seal 46 is disposed in a recess 48 and abuts the housing 16 to help provide a sealing function. There are also two gears mounted on the shafts 24,28; a drive gear 50 mounted on the drive shaft 24 and a driven or idler gear 52 mounted on the idler shaft 28. Both gears 50,52 are disposed in the cavity 20 (FIG. 2) when the pump 10 is fully assembled. Also disposed in the cavity 20 is a fixed wear plate 54 (FIG. 5) which is positioned between the cover plate 18 and the gears 50,52 when the pump is assembled, and a floating wear plate 56 is disposed between the gears 50,52 and the housing 16.

The floating plate 56 (FIG. 4) used in the pump 10 according to the present invention is made with a seal-groove 58 around the perimeter of an outer side 60 of the plate 56 such that a seal 62 (FIG. 3) is squeezed between the inside of a wall portion 64 (FIG. 4) of the groove 58 and the circumferential wall 66 (FIG. 2) of the gear cavity 20 in the housing 16. This is also referred to as a “side-seal” 62 (FIG. 3). The wall portion 64 (FIG. 4) of the seal groove 58 is made to have a predetermined height 68, so that the groove 58 accommodates considerable seal swelling within the height 68. Since the swelling is contained within the seal-groove 58, the seal 62 never comes in contact with the rear surface 70 (FIG. 2) of the gear cavity 20, so excessive swelling never forces the floating plate 56 (FIG. 3) up against the gears 50,52 (FIG. 5).

A flow orifice or flow aperture 72 (FIG. 4) extends through the floating plate 56, and is located in proximity to the outlet 12 of the pump 10 transmits pump outlet pressure to the outer side 60 (FIG. 4) of the plate 56. The outer side 60 of the plate 56 is the side of the plate 56 which faces away from the gears 50,52 (FIG. 5). The floating plate 56 also includes two clearance apertures 74, through which the shafts 24,28 (FIG. 5) extend. The entire area of the outer side 60 (FIG. 4) of the plate 56 (less the area of the two clearance apertures 74 in the plate 56 that the gear shafts 24,28 pass through) is acted on by pressure generated by the pump 10 to push the plate 56 such that the plate 56 applies a force to and is in contact with the gear faces 76 (FIG. 5).

The pump outlet pressure applied to the whole outer side 60 (FIG. 4) of the plate 56 is partially balanced by pump outlet pressure acting on part of the inner surface 84 (FIG. 6) of the plate 56. It can be seen in FIG. 6 that there is an axis 78 which extends longitudinally along the inner surface of plate 56. This axis 78 essentially divides the plate 56 in half, with one-half of the plate 56 functioning as a pump inlet-side half 80 (the half of the plate 56 associated with the inlet 14), and the other half functioning as a pump outlet-side half 82 (the half of the plate 56 associated with the outlet 12). The pump outlet pressure acting on the inner surface 84 only acts on the pump outlet-side half 82 of the inner surface 84, which balances off the pressure on the outer surface just below it. On the pump inlet-side half 80 of the plate 56 there is only pump inlet pressure, which is normally anywhere from a low vacuum to about five psi, so only pressure on the outer surface immediately below the area of this surface acts on this area to force the floating plate up against the gears 50,52. The net force applied to the plate 56 acting against the gear faces 76 (FIG. 5) has proven to be acceptable, as tested by drive shaft torque and durability testing. The drive shaft torque of the design of the present invention is just slightly more than that of the wear plates used in prior art designs.

The design incorporating the side-seal 62 (FIG. 3) of the present invention has significant advantages over prior art designs in that swelling of the seal 62 does not affect the performance of the pump 10. Furthermore, the exact thickness of the floating plate 56 is not critical, because the spacing of the floating plate 56 in relation to the rear surface 70 of the gear cavity 20 is irrelevant, thereby reducing the cost to manufacture the floating plate 56; also, the depth of the gear cavity is not as critical, thus less expensive to manufacture. The design of the present invention also allows for the floating plate 56 to move a large distance within the gear cavity 20 without diminishing the effectiveness of the seal 62; the pump 10 self-adjusts for considerable wear to the floating plate 56 and the faces 76 (FIG. 5) of the gears 50,52 in contact with the floating wear plate 56, as well as the faces 150 (FIG. 5) of the gears 50,52 in contact with the fixed wear plate 54; much more than is accommodated by prior art designs. The increased compensation for wear in the side plates 54,56 and faces 76,150 of the gears 50,52 helps to compensate for wear due to any dirt or rust that is sometimes in gasoline, especially when the gasoline is pumped from old steel storage tanks or old tanker trucks.

There is also a significant leakage path from the outlet pressure side, generally shown at 88 (FIG. 4), of the floating wear plate 56 back to the inlet pressure side 90 which occurs through the clearance between the outer wall 86 circumscribing the wear plate 56 and the circumferential wall 66 (FIG. 2) of the pump gear cavity 20. However, because the side-seal 62 (FIG. 3) is located in the groove 58 (FIG. 4) on the outer periphery of the plate 56 (as opposed to a groove on the outer surface 60 of the plate 56 on prior art pumps), the thickness of the outer wall 86 is reduced (as opposed to the outer wall 86 encompassing of the entire thickness of the plate 56), this in turn reduces the leaking path because there is a smaller area for the fluid to pass through, thus reducing the leakage. Any internal leakage from the outlet pressure side 88 of the pump 10 back to the inlet causes the pump 10 to have less positive displacement, and therefore creates a less desirable metering pump. Therefore, it is considered highly desirable to keep the leakage around the outer wall 86 of the plate 56 to a minimum

Also, any time fuel blows down from a high pressure to a low pressure, some of the fuel vaporizes, forming bubbles. These bubbles become smaller when they pass back through the gears to the outlet pressure side 88 (FIG. 4) of the pump, but they are still present; this affects the preciseness of the pump outlet flow, and the quality of the liquid flowing out of the pump (fuel with bubbles in it is considered “low quality” because it cannot be metered accurately). The flow should be as bubble-free as possible, and the configuration of the side-seal 62 (FIG. 3) in the seal groove 58 of the plate 56 significantly reduces the formation of bubbles in the fluid flowing through the pump 10.

Locating the shaft support bearings 32,42,37,45 (FIG. 5) in the housing 16 and cover plate 18 rather than in the wear plates 54,56 has several advantages, including but not limited to allowing the wear plates 54,56 to be much thinner as compared to prior art designs, thus reducing the leakage path around the wear plates 54,56, as discussed above. Positioning the bearings 32,42,37,45 in the housing 16 also locates the gears 50,52 in the cavity 20 more precisely, allowing a smaller clearance between the tips of the gear teeth 92 (FIG. 5) and the housing wall 20 (FIG. 2), thus a reduced leakage path. This enables a more positive displacement pump 10 and less vapor bubble formation, which improves the displacement and efficiency of the pump 10.

If the bearings 32,42,37,45 (FIG. 5) were to be positioned and supported by the wear plates 54 56, as opposed to the housing 16, the centers of the bearings 32,42,37,45 would be able to move because of the clearance between the wear plates 54,56 and the gear cavity wall 66. This would require some additional clearance between the tips of the gear teeth 92 and the circumferential wall 66 to compensate for any movement of the wear plates 54,56 (if the tolerances between the tips of the gear teeth 92 and the housing 16 are made tight enough to provide maximum positive displacement, the tips of the gear teeth 92 would cut into the circumferential wall 66 of the housing 16 excessively as the wear plate 56 moved during operation of the pump 10). This extra clearance between the tips of the gear teeth 92 (FIG. 5) and the circumferential wall 66 would reduce the output flow of the pump 10, thereby reducing efficiency, and promote more bubble formation.

The design of the side-seal 62 (FIG. 3) allows the floating plate 56 to move a significant amount within the housing 16 toward and away from the gear faces 76. If a piece of dirt or other debris comes between the gear faces 76 (FIG. 5) and the floating plate 56, the plate 56 is able to move away from the gear faces 76, allowing the particle to pass though, thus preventing a seizure of the pump 10. If dirt comes between the fixed wear plate 54 and the gear faces 150 (FIG. 5), the gears 50,52 and floating plate 56 move away from the fixed wear plate 54 to make room for the dirt to pass through. Pumps of the prior art with simple wear plates are susceptible to seizing when dirt was introduced with the fuel during testing. No pumps incorporating the side-seal 62 and floating plate 56 according to the present invention failed when dirt was introduced.

The floating plate 56 (FIG. 3) is biased towards the gears 50,52 by one or more resilient members, which in this embodiment are springs 94 (FIG. 2) each of which is disposed in a pocket 96, to keep the plate 56 in contact with the gear faces 76 (FIG. 5) when the pump 10 is shut off. Keeping the plate 56 in contact with the faces 76 of the gears 50,52 ensures that the pump 10 generates a pumping action as soon as the drive shaft 24 is rotated by an external source. The two pockets 96 are machined into the rear surface 70 of the gear cavity 20. The springs 94 are made to be long, and are then compressed enough so that the springs 94 are able to expand to accommodate considerable movement of the wear plate 56.

Because the outlet pressure of the pump 10 is introduced between the outer side 60 (FIG. 4) of the floating plate 56 and the rear surface 70 of the gear cavity 20, fluid is free to pass through the second shaft support bearing 42 (FIG. 5) and then build pressure against the pump drive shaft seal 98. The pressure against the pump drive shaft seal 98 because of the pressurized fluid generated by the pumping action created by the gears 50,52 must be limited. Too much pressure against the pump drive shaft seal 98 would shorten the life of the seal 98, and if the seal 98 were to fail, there would be a large leakage path for fuel to spill out of the pump 10.

To prevent excessive pressure from reaching the seal 98, a non moving pressure isolation sleeve 100 (FIG. 5) is positioned in the bore 22 adjacent the shaft support bearings 42 such that the sleeve 100 surrounds the drive shaft 24. The pressure isolation sleeve 100 includes a first groove 102 which receives a first seal 104, the first seal 104 fits into the bore 22 which also supports the second set of shaft support bearings 42. The non-moving pressure isolation sleeve 100 also includes a reduced diameter 106 formed around the circumference of the sleeve 100 which receives a second seal 108. The reduced diameter 106 positions the seal 108 into a receiver groove 110 on the outer side 60 (FIG. 4) of the floating plate 56. Some pressurized fuel on the outlet pressure side 88 of the floating plate 56 may still seep between the gear faces 76 (FIG. 5) and the inner surface 84 of the floating plate 56, then press against the shaft seal 98.

To provide additional prevention of pressure build up against the drive shaft seal 98, a channel 112 (FIG. 6) is formed as part of the inner surface 84 of the wear plate 56 to provide fluid communication between the area surrounded by the clearance aperture 74 through which the drive shaft 24 extends and an inlet notch 114 in fluid communication with the inlet 14 of the pump 10. This provides additional pressure relief to the drive shaft seal 98. This isolation of the pump outlet pressure from the pump drive shaft seal 98 significantly extends the life of the seal 98 and reduces potential leakage out of the pump 10.

Since substantially all of the pressure is eliminated from the second end 40 (FIG. 5) of the drive shaft 24, the pressure at the first end 34 of the drive shaft 24 must also be eliminated, or a net pressure will act on the first end 34 of the shaft 24 to undesirably force the gear face 76 of the drive gear 50 against the inner surface 84 of the floating wear plate 56. Reducing or eliminating pressure on the first end 34 of the drive shaft 24 is accomplished by a channel 116 (FIG. 7) formed on an inner surface 118 of the fixed wear plate 54, the channel 116 places an inlet notch 120 formed on the inner surface 118 of the fixed wear plate 54 in fluid communication with a clearance aperture 122 formed as part of the fixed wear plate 54, the clearance aperture 122 receives a portion of the drive shaft 24. This allows any pressure built up in the clearance aperture 122 to flow through the channel 116 and back to the inlet notch 120 formed as part of the fixed wear plate 54, and the inlet-pressure side 90 of the pump 10.

Because pump outlet pressure flows through the flow orifice 72 (FIG. 4) of the floating wear plate 56 to the area between the outer side 60 of the floating wear plate 56 and the rear surface 70 of the gear cavity 20, fluid is free to pass down through the second set of idler shaft support bearings 45 and then press on the second end 44 of the idler shaft 28. In one embodiment, this pressure could be eliminated by using another pressure isolation sleeve 100 in the same manner as described above with regard to the drive shaft 24, but this would be more costly. However, in this embodiment, pressure is also fed to the first end 38 of the idler shaft 28 to balance the pressure applied to the second end 44 of the idler shaft 28. The fluid is fed to the first end 38 by providing a channel 126 (FIG. 7) formed as part of the inner surface 118 which places an outlet notch 128 formed on the inner surface 118 of the fixed wear plate 54 in fluid communication with a clearance aperture 130; the clearance aperture 130 receives a portion of the idler shaft 28.

For the pump 10 to have precise positive displacement, the gears 50,52 must be fitted into the pump housing 16 so tightly that the tips of the gear teeth 92 have a maximum clearance of 0.0002 inches clearance to the circumferential wall 66 when the pump 10 is running under pressure. In most highly efficient, positive displacement pumps of prior art designs, the gears wear into the housing about 0.002 inches. This not only degrades the pump wall 66, but introduces dirt into the fuel system. To prevent distortion of the housing due to internal pressure, most prior art design pumps incorporate a massive housing in relation to the gear diameter the housing carries in an attempt to keep the gears from wearing excessively into the housing. To keep the gears 50,52 of the pump 10 from wearing excessively into the housing 16, the housing 16 distortion due to internal pressure must be extremely minimal. The pump 10 of the present invention minimizes distortion and mass for applications where the pump 10 is designed for the gears 50,52 having diameters up to about 2.250 inches.

The circumferential wall 66 of the housing 16 is substantially oval in shape. The housing 16 also has a horizontal axis 132 (FIG. 2) and a vertical axis 134. The present invention attains minimum distortion of the housing 16 through the use of more fasteners, with increased clamping force on each. In this embodiment, twelve studs 136 (FIG. 1) (not bolts) are used, with six studs 136 located above the horizontal axis 132 (FIG. 2) along the upper side of the circumferential wall 66, and six studs 136 located below the horizontal axis 132 along the lower side of the circumferential wall 66. Each stud 136 extends through a non-threaded aperture 138 (FIG. 9) formed in the cover plate 18, and into a threaded aperture 140 (FIG. 8) formed as part of a flange 142 on the housing 16. When assembled, the non-threaded apertures 138 of the cover plate 18 align with the threaded apertures 140 of the housing 16. The studs 136 provide more clamping force than bolts, and the six along each side of the circumferential wall 66 as shown in the Figures are much more effective than a symmetrically spaced bolt pattern. This pattern, combined with the high clamping forces, produces much less distortion than found in pumps of prior art designs because the cover 18 is clamped tight enough to the body that the walls that from the long sides of the oval gear cavity 66 (FIG. 2) cannot slide back and forth (distort) under the cover 18 (FIG. 1).

The front cover 18 (FIG. 9) includes a raised oval area 144 into which the recesses 30,36 (FIG. 5) are formed which have the bearings 32,37. The area surrounding the raised oval area 144 has the non-threaded apertures 138 and is of a reduced thickness compared to the raised oval area 144 to save weight and make the pump 10 more compact. However, to ensure the cover 18 has sufficient strength to further prevent distortion of the housing 16, four buttresses 146 (FIG. 9) are added and are connected to the raised oval area 144 provide enough rigidity to minimize distortion of the housing 16 resulting from internal pressure.

When the pump 10 is assembled, the first end 34 of the drive shaft 24 is disposed in the first recess 30 of the cover plate 18 and is supported by the first set of shaft support bearings 32, which are also disposed in the first recess 30. The first end 38 of the idler shaft 28 is disposed in the second recess 36 of the cover plate 18 and is supported by the first set of idler shaft support bearing 37, which are also disposed in the second recess 36. The second end 40 of the drive shaft 24 extends through the bore 22, the drive shaft seal 98, and out of the housing 16 such that the drive shaft 24 is connectable to a source of rotational power for driving the pump 10. The second end 40 of the drive shaft 24 is supported by the second set of shaft support bearings 42, which are also disposed in the bore 22 adjacent the pressure isolation sleeve 100 as shown in FIG. 5. The second end 44 of the idler shaft 28 is disposed in the recess 26 of the housing 16 and is supported by the second set of idler shaft support bearings 45, which are also disposed in the recess 26.

The fixed wear plate 54 is positioned in the housing 16 such that an outer surface 148 (FIG. 5) of the fixed wear plate 54 is adjacent to the cover plate 18, and the inner surface 118 of the fixed wear plate 54 is adjacent the faces 150 of the gears 50,52. In this position, the inlet notch 120 (FIG. 7) of the fixed wear plate 54 is in fluid communication with the inlet 14 and the outlet notch 128 is in fluid communication with the outlet 12.

On the opposite side of the gears 50,52, the floating wear plate 56 is positioned in the cavity 20 where the outer surface 60 (FIG. 4) is facing the rear surface 70 of the cavity 20 and receives a force from the springs 94. The springs 94 bias the floating wear plate 56 against the gears 50,52, and therefore the inner surface 84 against the gears 50,52. This positioning of the floating wear plate 56 in the cavity 20 places the inlet notch 114 of the floating wear plate 56 in fluid communication with the pump 10 inlet 14, and the outlet notch 124 is in fluid communication with the outlet 12 of the pump 10. The side-seal 62 (FIG. 3) is disposed between the wall portion 64 (FIG. 4) of the groove 58 and the circumferential wall 66 (FIG. 2) of the gear cavity 20 in the housing 16. The second seal 108 (FIG. 5) is positioned between the reduced diameter 106 of the non-moving pressure isolation sleeve 100 and the receiver groove 110 on the outer side 60 of the floating plate 56. Additionally, the first seal 104 is disposed in the first groove 102 of the pressure isolation sleeve 100 and is also pressed against the bore 22.

In operation, when the drive shaft 24 is not being rotated, the pump 10 does not generate any pumping action, and thus no pressure, and the springs 94 bias the floating wear plate 56 against the faces 76 of the gears 50,52, which biases the other faces 150 of the gears 50,52 against the fixed wear plate 54. When the drive shaft 24 is driven for rotation, the gears 50,52 (which are in mesh) rotate in a manner where fluid flowing in from the inlet 14 flows between the inlet notch 120 (FIG. 7) of the fixed wear plate 54 and the faces 150 of the gears 50,52, and fluid also flows between the inlet notch 114 (FIG. 6) of the floating wear plate 56 and the other faces 76 of the gears 50,52. The fluid then flows from both areas to between the gear teeth 92, where the fluid is compressed and forced (under pressure) into an area between the faces 76 (FIG. 5) of the gears 50,52 and the outlet notch 124 of the floating plate 56, and an area between the other faces 150 of the gears 50,52 and the outlet notch 128 of the fixed wear plate 54. The compressed fluid is forced out of the housing 16 through the outlet 12.

When the pump 10 is operating and fluid pressure is generated on the pump outlet-side half 82 of the plates 54,56, pressurized fluid passes through the flow orifice 72, this pressurizes the outer side 60 of the plate 56. This pressurization of the outer side 60 of the plate 56 maintains the contact of the wear plate 56 with the gears 50,52, and the contact of the gears 50,52 with the fixed wear plate 54, and continues to do so even after the plates 54,56 and gears 50,52 undergo wear throughout the life of the pump 10.

The pressure generated by the gears 50,52 is prevented from reaching the shaft seal 98 because of the sealing function provided by the pressure isolation sleeve 100 and the seals 104,108. If any pressurized fluid seeps between the floating wear plate 56 and the face 76 of the drive gear 50, the fluid flows back to the area between the inlet notch 114 (FIG. 4) of the floating wear plate 56 and the faces 76 of the gears 50,52 via the channel 112. Additionally, any pressurized fluid is prevented from building on the first end 34 of the drive shaft 24, the recess 30, or from seeping between the fixed wear plate 54 and the face 150 of the drive gear 50 because of the channel 116 formed on the inner surface 118 of the fixed wear plate 54; the fluid flows through the channel 116 back to the area between the inlet notch 120 formed on the inner surface 118 of the fixed wear plate 54 and the faces 150 of the gears 50,52.

As discussed above, the idler shaft 28 is pressure balanced (as opposed to the drive shaft 24, which has no pressure applied to either end 34,40), where pressure acts on both ends 38,44 of the idler shaft 28. The pressurized fluid that flows through the flow orifice 72 (FIG. 6) and acts on the floating wear plate 56 also flows into the recess 26 (FIG. 5) and around the second set of idler shaft support bearings 45, applying pressure to the second end 44 of the idler shaft 28. This pressure is balanced by the fluid flowing under pressure from the area between the outlet notch 128 of the fixed wear plate 54 and the faces 150 of the gears 50,52 through the channel 126, and then through the clearance aperture 130 surrounding the idler shaft 28 and into the recess 36, where the fluid builds pressure on the first end 38 of the idler shaft 28, counter-acting the pressure on the second end 44 of the idler shaft 28.

The present invention provides a highly efficient, positive displacement pump 10 for use with various commercial automotive and racing applications, and is particularly suited for use with fluids having low viscosity due to the tight tolerances of the gears 50,52 in relation to one another, and in relation to the circumferential wall 66, as well as the plates 54,56.

The description of the invention is merely exemplary in nature and, thus, variations that do not depart from the gist of the invention are intended to be within the scope of the invention. Such variations are not to be regarded as a departure from the spirit and scope of the invention. 

1. A fuel pump, comprising: a housing having a cavity, said cavity having a rear surface; a drive gear disposed in said cavity; a driven gear disposed in said cavity and in mesh with said drive gear for pressurizing fluid flowing into said housing; a floating wear plate having an inner side adjacent and in contact with said drive gear and said driven gear; a fixed wear plate having an inner surface adjacent and in contact with said drive gear and said driven gear; and a flow orifice formed as part of said floating wear plate such that a portion of said pressurized fluid flows through said flow orifice and between said rear surface of said cavity and said floating wear plate, causing said floating wear plate to apply force to said drive gear and said driven gear, and therefore causing said drive gear and said driven gear to apply force to said fixed wear plate, thereby compensating for any wear of said drive gear, said driven gear, said floating wear plate, and said fixed wear plate.
 2. The fuel pump of claim 1, further comprising: a groove formed on an outer periphery of said floating wear plate; and a seal disposed in said groove formed on said outer periphery of said floating wear plate, primarily to seal the wear plate to the gear cavity wall, but also said seal operable to substantially prevent pressurized fluid from flowing around the outer periphery of said floating wear plate.
 3. The fuel pump of claim 2, further comprising a circumferential wall surrounding said drive gear and said driven gear, said drive gear and said driven gear being in minimal clearance with said circumferential wall, said seal is in contact with said circumferential wall to substantially prevent pressurized fluid from flowing around the outer periphery of said floating wear plate.
 4. The fuel pump of claim 1, further comprising: a drive shaft extending through a bore formed as part of said housing, said drive gear mounted on said drive shaft; and an idler shaft extending into a recess formed as part of said housing, said driven gear mounted on said idler shaft.
 5. The fuel pump of claim 4, further comprising a non-moving pressure isolation sleeve circumscribing said drive shaft, said pressure isolation sleeve partially disposed in said bore and partially disposed in said gear cavity for substantially preventing fluid from flowing into said bore.
 6. The fuel pump of claim 5, said pressure isolation sleeve further comprising: a first groove formed as a part of said pressure isolation sleeve disposed in said bore; a reduced diameter formed as a part of said pressure isolation sleeve disposed in said gear cavity; a first seal disposed in said first groove for preventing fluid from flowing into said bore; and a second seal disposed in said reduced diameter and a receiver groove formed on said outer side of said floating wear plate for preventing fluid from flowing around a portion of said drive shaft extending through said floating wear plate.
 7. The fuel pump of claim 1, further comprising: an inlet formed as part of said housing; an inlet notch formed on said inner side of said floating wear plate such that fluid flowing into said housing from said inlet flows between said inlet notch formed as part of said floating wear plate as well as said drive gear and said driven gear; and an inlet notch formed on said inner surface of said fixed wear plate such that fluid flowing into said housing from said inlet flows between said inlet notch formed as part of said fixed wear plate as well as said drive gear and said driven gear.
 8. The fuel pump of claim 1, further comprising: an outlet formed as part of said housing; an outlet notch formed on said inner side of said floating wear plate such that said fluid pressurized by said drive gear and said driven gear flows between said outlet notch formed as part of said floating wear plate as well as said drive gear and said driven gear to said outlet of said housing; and an outlet notch formed on said inner surface of said fixed wear plate such that said fluid pressurized by said drive gear and said driven gear flows between said outlet notch formed as part of said fixed wear plate as well as said drive gear and said driven gear to said outlet of said housing, said drive gear and said driven gear operable for pressurizing said fluid.
 9. A fuel pump, comprising: a housing having a cavity, said cavity having a rear surface and a circumferential wall; a drive gear disposed in said cavity; a driven gear disposed in said cavity and in mesh with said drive gear for pressurizing fluid flowing into said housing; a floating wear plate having an inner side adjacent and in contact with said drive gear and said driven gear; a groove formed on the outer periphery of said floating wear plate; a seal disposed in said groove formed on said outer periphery of said floating wear plate such that said seal is in contact with said circumferential wall for substantially preventing fluid flow around the outer periphery of said floating wear plate; a fixed wear plate having an inner surface adjacent and in contact with said drive gear and said driven gear; and a flow orifice formed as part of said floating wear plate such that a portion of said pressurized fluid flows through said flow orifice to pressurize the space between said rear surface of said cavity and said floating wear plate, causing said floating wear plate to apply pressure to said drive gear and said driven gear, and causing said drive gear and said driven gear to apply pressure to said fixed wear plate, thereby compensating for any wear of said drive gear, said driven gear, said floating wear plate, and said fixed wear plate.
 10. The fuel pump of claim 9, further comprising: an inlet formed as part of said housing; an inlet notch formed on said inner side of said floating wear plate such that fluid flowing into said housing from said inlet flows between said inlet notch formed as part of said floating wear plate as well as said drive gear and said driven gear; and an inlet notch formed on said inner surface of said fixed wear plate such that fluid flowing into said housing from said inlet flows between said inlet notch formed as part of said fixed wear plate as well as said drive gear and said driven gear.
 11. The fuel pump of claim 9, further comprising: an outlet formed as part of said housing; an outlet notch formed on said inner side of said floating wear plate such that said fluid pressurized by said drive gear and said driven gear flows between said outlet notch formed as part of said floating wear plate as well as said drive gear and said driven gear to said outlet of said housing; and an outlet notch formed on said inner surface of said fixed wear plate such that said fluid pressurized by said drive gear and said driven gear flows between said outlet notch formed as part of said fixed wear plate as well as said drive gear and said driven gear to said outlet of said housing, said drive gear and said driven gear operable for pressurizing said fluid.
 12. The fuel pump of claim 11, said flow orifice is formed as part of said outlet notch formed on said inner side of said floating wear plate.
 13. The fuel pump of claim 9, further comprising: a drive shaft extending through a bore formed as part of said housing, said drive gear mounted on said drive shaft; and an idler shaft partially extending into a recess formed as part of said housing, said driven gear mounted on said idler shaft such that said drive gear is in mesh with said driven gear.
 14. The fuel pump of claim 13, further comprising a non-moving pressure isolation sleeve circumscribing said drive shaft, said pressure isolation sleeve partially disposed in said bore and partially disposed in said gear cavity for substantially preventing fluid from flowing into said bore.
 15. The fuel pump of claim 14, said pressure isolation sleeve further comprising: a first groove formed as a part of said non moving-pressure isolation sleeve disposed in said bore; a reduced diameter formed as a part of said non-moving pressure isolation sleeve disposed in said gear cavity; a first seal disposed in said first groove for preventing fluid from flowing into said bore; and a second seal disposed in said notch and a receiver groove formed on said outer side of said floating wear plate for preventing fluid from flowing around a portion of said drive shaft extending through said floating wear plate.
 16. The fuel pump of claim 9, wherein said drive gear and said driven gear are at minimal clearance with said circumferential wall of said housing.
 17. A fuel pump, comprising: a housing having an inlet, an outlet, and a gear cavity, said gear cavity having a rear surface and a circumferential wall; a drive gear mounted on a drive shaft, said drive gear disposed in said gear cavity, said drive shaft extending into a bore formed as part of said housing; a driven gear mounted on an idler shaft, said driven gear disposed in said gear cavity and in mesh with said drive gear, said circumferential wall substantially surrounding said drive gear and said driven gear such that said drive gear and said driven gear are in minimal clearance with said circumferential wall; a floating wear plate having an inner side adjacent and in contact with said drive gear and said driven gear; a groove formed on an outer periphery of said floating wear plate; a side seal disposed in said groove and in contact with said circumferential wall of said gear cavity, primarily to seal the wear plate to the gear cavity walls, but also to substantially prevent pressurized fluid from flowing around the outer periphery of said floating wear plate; a fixed wear plate having an inner surface adjacent and in contact with said drive gear and said driven gear; a flow orifice formed as part of said floating wear plate such that fluid flows through said pump inlet and into said gear cavity and said drive gear and said driven gear rotate to create a pumping action to force a portion of said fluid out of said outlet, and a portion of fluid through said flow orifice to pressurize said gear cavity between said floating wear plate and said rear surface of said gear cavity, maintaining said floating wear plate in contact with said drive gear and said driven gear, as well as maintaining said fixed wear plate in contact with said drive gear and said driven gear to compensate for wear of said floating wear plate, said fixed wear plate, said drive gear, and said driven gear.
 18. The fuel pump of claim 17, further comprising: an inlet notch formed on said inner side of said floating wear plate such that fluid flowing into said housing from said inlet flows between said inlet notch formed as part of said floating wear plate as well as said drive gear and said driven gear; an inlet notch formed on said inner surface of said fixed wear plate such that fluid flowing into said housing from said inlet flows between said inlet notch formed as part of said fixed wear plate as well as said drive gear and said driven gear; an outlet notch formed on said inner side of said floating wear plate such that said fluid pressurized by said drive gear and said driven gear flows between said outlet notch formed as part of said floating wear plate as well as said drive gear and said driven gear to said outlet of said housing; and an outlet notch formed on said inner surface of said fixed wear plate such that said fluid pressurized by said drive gear and said driven gear flows between said outlet notch formed as part of said fixed wear plate as well as said drive gear and said driven gear to said outlet of said housing, said drive gear and said driven gear operable for pressurizing said fluid.
 19. The fuel pump of claim 17, further comprising a non-moving pressure isolation sleeve circumscribing said drive shaft, said non-moving pressure isolation sleeve partially disposed in said bore and partially disposed in said gear cavity for substantially preventing fluid from flowing into said bore.
 20. The fuel pump of claim 19, said non-moving pressure isolation sleeve further comprising: a first groove formed as a part of said non-moving pressure isolation sleeve disposed in said bore; a reduced diameter formed as a part of said non-moving pressure isolation sleeve disposed in said gear cavity; a first seal disposed in said first groove for preventing fluid from flowing into said bore; and a second seal disposed in said notch and a receiver groove formed on said outer side of said floating wear plate for preventing fluid from flowing around a portion of said drive shaft extending through said floating wear plate. 